Safety device monitoring system

ABSTRACT

For use in monitoring a safety device switch through which alternating current flows, monitoring means comprising a rectifier connected across such a switch to provide a direct current output when the switch is opened, a light and a capacitor connected in series across the output of the rectifier, a signal light, and a light-actuated silicon controlled rectifier. The silicon controlled rectifier is positioned and arranged to be actuated or rendered conductive by light from the light which is in series with the capacitor. When the safety device switch is opened, direct current provided by the rectifier charges the capacitor to a predetermined level. During this charging process, the light in series with the capacitor produces light for actuating the silicon controlled rectifier. The power source for the signal light and the silicon controlled rectifier may be a separate, low voltage direct current power source completely separate from the power source producing the current flowing through the safety device switch.

United States Patent Lavelle [451 Oct. 3, 1972 [72] Inventor: Michael R.Lavelle, 9331 North Delaware St., Indianapolis, 1nd. 46240 [22] Filed:June 21, 1971 [21] Appl. No.: 154,734

[52] US. Cl. ..340/252 R, 340/213 R, 340/236, 340/240, 340/256 [51] Int.Cl. ..G08b 21/00 [58] Field of Search ..340/248, 250, 252, 256, 253,340/213 R, 415, 255; 200/167; 317/9 D, 36 TD; 307/92-94, 131

Monigal et al. 3.340/415 X Edson ..340/255 X Primary Examiner-John W.Caldwell Assistant Examiner-Daniel Myer Attorney-Hood, Gust, lrish,Coffey & Lundy [57] ABSTRACT For use in monitoring a safety deviceswitch through which alternating current flows, monitoring meanscomprising a rectifier connected across such a switch to provide adirect current output when the switch is opened, a light and a capacitorconnected in series across the output of the rectifier, a signal light,and a light-actuated silicon controlled rectifier. The siliconcontrolled rectifier is positioned and arranged to be actuated orrendered conductive by light from the light which is in series with thecapacitor. When the safety device switch is opened, direct currentprovided by the rectifier charges the capacitor to a predeterminedlevel. During this charging process, the light in series with thecapacitor produces light for actuating the silicon controlled rectifier.The power source for the signal light and the silicon controlledrectifier may be a separate, low voltage direct current power sourcecompletely separate from the power source producing the current flowingthrough the safety device switch.

9 Claims, 1 Drawing Figure PATENTEDUETIi 1972 3,696,364

LII

INVENTOR.

MICHAEL R. LAVELLE HOOD,GUST, IRISH, LUNDY & COFFEY SAFETY DEVICEMONITORING SYSTEM This invention relates to safety device switches, andmore particularly to the provision of economical and reliable andeffective means for monitoring the condition of such switches.

It is a primary object of my invention to provide means for monitoring asafety device switch, or any switch through which alternating currentflows, and

providing a signal when that switch has been, for some reason, opened.My system includes a sensing portion and signaling portion isolated fromeach other in a manner such that disturbances or failures in one portionwill not result in a disturbance or failure in the other portion.Isolation electrically and mechanically is achieved by constructing thetwo portions such that the signaling portion is operated by lightproduced by the sensing portion. One objective of my invention is tohave the signaling portion energized by a low voltage direct currentpower source which is completely separated from the power sourceproducing the current flowing through the safety device switch.

My invention, therefore, comprises means for use in monitoring a switchthrough which alternating current flows, the monitoring means includingrectifier means connected across such a switch to provide a directcurrent output when the switch is opened. The rectifier means is,therefore, a primary portion of my sensing system. Light means andcapacitance means are connected to the output of the rectifier means toprovide a light output when the switch being monitored is opened. 6

The signaling portion of my system includes a signal means, such as asignal light or a bell, and light-actuated switch means for energizingthe signaling means, the light-actuated switch means being positionedand arranged to be actuated by light from the light means connected tothe rectifier means.

My monitoring means includes means for providing a low voltage directcurrent power source separate from the alternating current sourceproducing the current flow through the switch being monitored. The saidsignal means and light-actuated switch means are connected in seriesacross the direct current source such that the light-actuated switchmeans is rendered conductive by light to energize the signal means. Thelightactuated switch means is a latching-type switch means such thatonce it is rendered conductive, it will stay conductive continuously toenergize the signal means until the direct current source is removedfrom the anode of the switch means.

In the illustrative embodiment, the rectifier means includes a full-waverectifier, the light means and capacitance means being connected inseries across the output of the rectifier such that the light means isignited by direct current flow when the monitored switch is opened untilthe capacitance means is charged to a predetermined level. Once thecapacitance means is charged to such a predetermined level, current willnot flow through the light means.

While I have shown and described only one monitoring means for oneswitch, it will be appreciated that I may provide a pluralityof suchmonitoring means for monitoring a plurality of such switches. I mayplace the monitoring means on a conventional control panel for viewingby maintenance personnel. The packaging of the components of mymonitoring means may be accomplished to suit the particular monitoringapplication. As will be discussed hereinafter, since the operativeconnection between the sensing portion of my system and the signalingportion of my system is accomplished by light, the packaging shouldprovide for proper optical shielding to prevent energization of thesignaling portion by light not produced by the sensing portion.

Other objects and features of my present invention will be discussedhereinafter.

To the accomplishment of the above and related objects, my invention maybe embodied in the form illustrated in the accompanying drawings,attention being called to the fact, however, that the drawings areillustrative only, and that change may be made in the specificconstruction illustrated and described, so long as the scope of theappended claims is not violated.

in the drawing:

The single FIG. is a schematic view of a portion of a typical operatingsystem including a safety device switch and my monitoring meansmonitoring that switch.

Turning now to the drawing, it will be seen that I have shownalternating current terminals 10, 12. These terminals may be connected,for instance, to a l 10 volt alternating current power source. I havealso illustrated terminals 14, 16 across which is connected the coil ofa relay 18, the terminals l4, l6 representing, for instance, another orthe same alternating current power source. In series with the coil ofthe relay 18 is a control switch 20 which may be, for instance, aconventional thermostat switch. The relay 18 operates a switch 22 whichis in parallel with another switch 24 operated by a load relay 26. Whenthe switch 20 is closed, the relay l8 closes the switch 22. The coil ofthe load relay 26 is connected across the power terminals 10, 12. Therelay 26 also operates another switch 28 which closes a circuit betweenpoints 30 and 32. The mechanical connection between the relay 26 and theswitches 24, 28 is shown by dashed lines. In series with the coil of therelay 26 is a safety device switch 34 which is normally closed. Also inseries with the coil of the relay 26 and the switch 34 is the otherswitch 24 operated by the relay 26.

A full wave rectifier, indicated generally at 36 and comprising diodes38, 40, 42 and 44 connected in a conventional fashion is connected inparallel with the switch 34. Across the output terminals 46, 48 of thisbridge rectifier is a series circuit including a capacitor 50 and a neonlamp 52.

The switch 34, which is normally closed, is the safety device switchbeing monitored. If, for some reason, this switch opens, the full wavebridge rectifier 36 will apply a direct current potential across theterminals 46, 48 to charge the capacitor 50. The voltage required tocharge this capacitor 50 is sufficient to ignite the neon lamp 52. Theignition of the neon lamp 52 produces light as indicated by the arrows54. This light is directed at the light sensitive surface of alight-actuated silicone controlled rectifier 56.

The rectifier 56 is an electronic switch which completes the circuitacross a low voltage source indicated at terminals 58, 60, the terminal60 representing the positive side of the low voltage source. There is alamp 62 connected between the anode of the rectifier 56 and the terminal60 so that, when the rectifier turns on, current can flow from theterminal 60 through the lamp 62 and the anode-cathode circuit of the SCR56 to the ground terminal indicated at 58. The gate circuit of the SCR56 is connected via a resistor 64 to ground as illustrated.

l have referred to the load relay 26 as being the relay which actuatesthe load switch 28 to energize, for instance, the cooling motorcontactor of a chiller or some other such device. This-control systemcan be used with any number of systems such as heating systems andcooling systems. While I have indicated that the switch 20 may be athermostat, it may be any type of control element such as a humidistat,pressure sensing switch, etc. The function of the switch 20 is to closea circuit upon a happening such as an increase in temperature or adecrease in temperature.

When the switch 34 opens, thevcharge builds up on the capacitor 50thereby causing current to stop flowing from terminal to terminal 12. Inthis way, normal operation of the safety device switch 34 is permitted.

Particularly, the function of the'safety device switch 34, when itopens, is to drop the load relay 26 out. It will be appreciated that,when the switch 34 opens, an alternating current voltage is applied tothe rectifier 36 to produce a direct current voltage to charge thecapacitor 50. Once this capacitor 50 is charged to a prescribed level,current will no longer flow through the bridge network and across theterminals 10 and 12 to hold the relay 26 in. That is, when the voltageappears across terminals- 46 and 48, lamp 52 will immediately ignite andstay lit until capacitor 50 is charged to its maximum capacity. When thecapacitor 50 is charged to its prescribed. level, current will not flowbetween the points 46, 48 and then the lamp 52 will not be ignited.

The SCR 56 is a latching-type SCR in that, once it is turned on bylight, it will not turn off until the voltage is removed from its anode.Thus lamp 62 will continue to stay lit even if switch 34 goes to theclosed position. In this way a service technician can recognize thespecific safety switchthat opened even though it has gone to the closedposition.

An important advantage of this system is that. the monitoring circuitincluding the SCR 56 and lamp 62 are operated from a separate, lowvoltage source, not involved with the power source across the terminals10 and 12 or the terminals 14, 16.

The only connection between the monitoring system and the control systemis the light emitted from the lamp 52 and directed at the rectifier 56.There is no other mechanical or electrical connection. This gives goodisolation characteristics to assure reliability of the monitoring systemand, importantly, to prevent any type of reaction between the monitoringsystem and the control system.

The switch 34 can be a safety device such as high pressure control, oilpressure control, flame safety control, low water control, etc. Theswitch 28 may be a switch for operating any type of appliance such as amotor, compressor, gas valve, etc. I

Relayswitch 24 is mechanically held closed by load relay 26 and therebycompletes the circuit between terminals l0 and 12 even if switch 22moves to the open position. Thereby, when switch 34 opens, the loadrelay 26 drops out causing switch 24 to open. The load relay 26 may notbe energized again unless switch 20 closes.

In recapitulation, when switch 20 is closed, relay 18 operates to closeswitch 22. Then, if safety switch 34 is closed, i.e., normal operatingconditions exist, current will flow from terminals 10 and 12 to energizerelay 26 which, in addition to closing load contacts such as the contact28, closes the switch 24. Once the switch 24 is closed, i.e., the relay26 is energized, the switch 22 may open because of a lack of currentthrough the coil of the relay 18 caused by-opening of the switch 20.Upon opening of switch 34 due to a happening such as a loss of pressure,a loss of flame, etc., current must stop flowing between the terminals10 and 12 thereby to cause relay 26 to drop out. In this way, the safetyswitch 34 prevents normal operation. With sensor wires 66, 68 connectedacross switch 34, the full wave bridge rectifier 36 is connected inparallel across switch '34. When switch 34 opens, the alternatingcurrent across terminals l0, 12 is impressed across rectifier 36 and,therefore, across terminals 46, .48. Direct current then flows throughthe lamp 52 and intothe capacitor 50. The neon lamp 52 ignites and stayslit until capacitor 50 is fully charged, at which time direct currentand, therefore, alternating current between terminals l0, 12 stopsflowing. In this arrangement, therefore, the safety device monitoringsystem senses when a safety switch, such as switch 34, opens upon afailure .to operate normally but the monitoring system does notinterfere with the normal operation of the system being monitored.

The safety switch 34 need not be in series with switches 22, 24 and thecoil of the relay 26. The switch 34 may be", for instance, only inseries with the coil of the relay 26 or switch 24. In any case, theswitch 34 is to interrupt the flow of alternating current in a circuitthereby to act as a safety device.

What is claimed is:

1. In combination, a circuit for connection across an alternatingcurrent power source comprising a safety switch through whichalternating current flows, load switch means connected to said safetyswitch and dominated thereby, and means for monitoring said safetyswitch, said monitoring means including rectifier means connected acrosssaid safety switch, said rectifier means including direct current outputterminals, light means and capacitance means connected across saidoutput terminals, signal means, and light-actuated switch means forconnecting said signal means to a second-power source, saidlight-actuated switch means being positioned and arranged so that itslight sensitive surface receives light from said light means, saidlightactuated switch means being rendered conductive by such light toenergize said signal means.

2. The combination of claim 1 in which said rectifier means includes afull wave rectifier, said light means and capacitance means beingconnected in series such that said light means is ignited by currentflow when said safety switch is open until said capacitance means ischarged to a predetermined level, and said light-actuated switch meansincluding a latching-type light-actuated silicon controlled rectifier.

3. The combination of claim 2 in which said signal means includes alight connected in series with the anode-cathode electrodes of saidsilicon controlled rectifier, said silicon controlled rectifier beingarranged to conduct low voltage direct current from such a second sourceto energize said light.

4. The combination of claim 2 in which said light means includes a neonlamp.

5. For use in monitoring a switch through which alternating currentflows, monitoring means comprising rectifier means connected across sucha switch to provide a direct current output when the switch is opened,light means and capacitance means connected across the output of saidrectifier means, signal means, and light-actuated switch means forenergizing said signal means, said light-actuated switch means beingpositioned and arranged to be actuated by light from said light means.

6. The monitoring means of claim 5 including means for providing a lowvoltage direct current power source separate from such an alternatingcurrent source, said signal means and light-actuated switch means beingconnected in series across the direct current source such that saidlight-actuated switch means is rendered conductive by light to energizesaid signal means.

7. The monitoring means of claim 5 in which said rectifier meansincludes a full wave rectifier, said light means and capacitance meansbeing connected in series such that said light means is ignited bydirect current flow when the monitored switch is opened until saidcapacitance means is charged to a predetermined level, saidlight-actuated switch means including a latching-type light-actuatedsilicon controlled rectifier.

8. The monitoring means of claim 6 in which said rectifier meansincludes a full wave rectifier, said light means and capacitance meansbeing connected in series such that said light means is ignited bydirect current flow when the monitored switch is opened until saidcapacitance means is charged to a predetermined level, saidlight-actuated switch means including a latching-type light-actuatedsilicon controlled rectifier.

9. The monitoring means of claim 8 in which said signal means includes alight connected in series with the anode-cathode electrodes of saidsilicon controlled rectifier, said silicon controlled rectifier beingarranged to conduct low voltage direct current to energize said light.

1. In combination, a circuit for connection across an alternatingcurrent power source comprising a safety switch through whichalternating current flows, load switch means connected to said safetyswitch and dominated thereby, and means for monitoring said safetyswitch, said monitoring means including rectifier means connected acrosssaid safety switch, said rectifier means including direct current outputterminals, light means and capacitance means connected across saidoutput terminals, signal means, and light-actuated switch means forconnecting said signal means to a second power source, saidlight-actuated switch means being positioned and arranged so that itslight sensitive surface receives light from said light means, saidlight-actuated switch means being rendered conductive by such light toenergize said signal means.
 2. The combination of claim 1 in which saidrectifier means includes a full wave rectifier, said light means andcapacitance means being connected in series such that said light meansis ignited by current flow when said safety switch is open until saidcapacitance means is charged to a predetermined level, and saidlight-actuated switch means including a latching-type light-actuatedsilicon controlled rectifier.
 3. The combination of claim 2 in whichsaid signal means includes a light connected in series with theanode-cathode electrodes of said silicon controlled rectifier, saidsilicon controlled rectifier being arranged to conduct low voltagedirect current from such a second source to energize said light.
 4. Thecombination of claim 2 in which said light means includes a neon lamp.5. For use in monitoring a switch through which alternating currentflows, monitoring means comprising rectifier means connected across sucha switch to provide a direct current output when the switch is opened,light means and capacitance means connected across the output of saidrectifier means, signal means, and light-actuated switch means forenergizing said signal means, said light-actuated switch means beingpositioned and arranged to be actuated by light from said light means.6. The monitoring means of claim 5 including means for providing a lowvoltage direct current power source separate from such an alternatingcurrent source, said signal means and light-actuated switch means beingconnected in series across the direcT current source such that saidlight-actuated switch means is rendered conductive by light to energizesaid signal means.
 7. The monitoring means of claim 5 in which saidrectifier means includes a full wave rectifier, said light means andcapacitance means being connected in series such that said light meansis ignited by direct current flow when the monitored switch is openeduntil said capacitance means is charged to a predetermined level, saidlight-actuated switch means including a latching-type light-actuatedsilicon controlled rectifier.
 8. The monitoring means of claim 6 inwhich said rectifier means includes a full wave rectifier, said lightmeans and capacitance means being connected in series such that saidlight means is ignited by direct current flow when the monitored switchis opened until said capacitance means is charged to a predeterminedlevel, said light-actuated switch means including a latching-typelight-actuated silicon controlled rectifier.
 9. The monitoring means ofclaim 8 in which said signal means includes a light connected in serieswith the anode-cathode electrodes of said silicon controlled rectifier,said silicon controlled rectifier being arranged to conduct low voltagedirect current to energize said light.